Plastic Bearing Bushing With Bulges For Thermal Stress Relief
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Solution Overview
Problem
Existing plastic bearing bushes for electrical machines, particularly in centrifugal pumps, face issues due to their higher expansion coefficient compared to bearings, leading to play and mechanical stress at varying temperatures, causing vibration, noise, and wear, and a weakening press bond over time.
Innovation Solution
A bearing bush with a cylindrical plastic wall featuring sector sections and radially outward bulges, allowing for a force-fitting interference fit that distributes stress uniformly and allows for elastic deformation, eliminating the need for additional fasteners and enhancing heat dissipation and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic bearing bush is used to fasten a bearing, then the bearing can be held in place, but at high temperatures the press joint is released causing play and vibration
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the bearing bush wall, specifically introducing variable wall thickness with bulges and troughs. This geometric parameter modification allows the plastic material to better accommodate thermal expansion and contraction, maintaining the press joint between the bearing and bush across a wide temperature range from -40°C to +120°C without releasing fixation or causing play.
2Strength
If the wall thickness is increased to strengthen the bearing bush, then mechanical strength is improved, but the bush becomes more prone to breaking at low temperatures
Solution Approach 1:
The patent applies local quality by creating non-uniform wall thickness distribution through bulges and troughs. The wall thickness varies locally along the axial direction, with thicker sections (bulges) providing enhanced strength where needed and thinner sections (troughs) reducing overall mass and stress concentration. This local variation optimizes the balance between mechanical strength and low-temperature brittleness.
3Reliability
If additional fasteners are used to secure the bearing, then fixation reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by integrating the fixation function directly into the bearing bush structure itself. The bulges and troughs formed as integral parts of the bush wall create a self-contained fixation mechanism that eliminates the need for separate fasteners, retaining rings, or additional securing components. This unified design maintains high fixation reliability while significantly reducing device complexity.
4Reliability
If the press bond is strengthened to prevent play, then bearing fixation is improved, but the bushing experiences increased mechanical stress and may break
Solution Approach 1:
The patent applies segmentation by dividing the continuous bearing bush wall into alternating bulges and troughs along the axial direction. This segmentation creates multiple localized contact zones between the bearing and bush, distributing the press bond forces across several regions rather than concentrating stress in a single continuous wall. The troughs act as stress relief zones, reducing overall mechanical stress on the bushing while maintaining secure bearing fixation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a permanent radial and axial seat for the bearing, reducing mechanical stress, preventing vibration and noise, and maintaining a secure fit without additional fasteners, while allowing medium flow and heat dissipation, thus improving the durability and performance of the bearing assembly.
Implementation Method 1
the bearing bushing is elastic and non-destructive depending on these stresses and forces can deform both in the case of expansion and contraction
Implementation Method 2
they have a much larger expansion coefficient than the material from which the bearing is made. This means that at high temperatures caused by friction on the bearing, but especially due to a high temperature of the medium conveyed by the pump
Implementation Method 3
whose radially inner sides form contact surfaces, between which the bearing can be held in a force-fitting manner
Implementation Method 4
the pumped medium flushes the bearings and the corresponding bearing bushes
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The bearing bush comprises a cylindrical wall (3) made of plastic, where the cylindrical wall surrounds a bearing in its inserted state and comprises sector portions (4) whose radial inner sides form bearing surfaces (5), between which the bearing is positively preserved. The wall between the sector portions comprises radially outwardly directed convexities. The wall is closed peripherally. The convexities are formed by cylindrical arc portions of the wall. A radius of curvature of the arc portions is smaller than a distance of the bearing surface to a bearing bush axis (8). The bearing bush comprises a cylindrical wall (3) made of plastic, where the cylindrical wall surrounds a bearing in its inserted state and comprises sector portions (4) whose radial inner sides form bearing surfaces (5), between which the bearing is positively preserved. The wall between the sector portions comprises radially outwardly directed convexities. The wall is closed peripherally. The convexities are formed by cylindrical arc portions of the wall. A radius of curvature of the arc portions is smaller than a distance of the bearing surface to a bearing bush axis (8), and is between four and six-tenth of this distance. The wall is present in a circumferential direction, where the bearing surfaces are formed by the inner side of wave troughs. The wall comprises recesses, which are distributed at equal angular intervals to each other. A thickness of the wall of the sector portions is partially larger than the thickness of the wall between the sector portions. The bearing bush further comprises a bottom (9), with the wall is integrally formed. The bottom comprises a spacer at which the bearing is present in an inserted state. The sector portions are elongated in an axial extension direction with respect to the wall in a region of the convexities and comprise a detent for engaging the bearing at their open ends. The bearing surfaces of the sector portions of the wall are slightly inclined in an axial direction to the bearing bush axis, and deviate at an angle of 0.05-5[deg] C for the bearing bush axis. The bearing surfaces are formed in a concave manner. The distance of the bearing surfaces to the bearing bush axis is 0.5-1 mm smaller than the outer radius of the bearing. The wall or the bottom comprises a projection at its side facing towards the bearing bush axis, where the projection is enclosed in the recess of the bearing in its inserted state.